This invention relates to systems for pumping water-borne solid articles such as fish, marine crustacea and others, and is herein illustratively described by reference to the presently preferred form thereof as applied to pumping fish. It will be recognized, however, that certain modifications and changes with respect to details may be made, and that the invention may be used in other applications without departing from the essential features involved.
Fish and other food articles have been pumped with water through conduits by a variety of techniques. One in use employs a submersible on-line centrifugal pump through which the articles must pass. Such pumps are in commercial use to brail herring and other small fish from fishing nets, to transfer fish from the flooded holds of fishing vessels to receiving tanks in processing plants, and in similar applications. However, attempts to use such pumps of practical size for larger fish or more delicate forms of marine life can present problems due to flesh damage.
In air lift pumping, air under pressure is injected into the vertical run of a water primed siphoning conduit so as to lift the water and articles borne by the water through the conduit. These pumps, requiring no moving parts within the transfer path, have a gentle action. However, their pumping height capability is too limited for many applications. Attempts to achieve increased lift by lowering the inlet end of the conduit further below the water's surface is limited by physical constraints in most cases.
Water jet pumps are also in use. These pumps can move a column of water carrying solid articles to considerable heights and, like air lift pumps, operate without necessity of the articles passing through a mechanical impeller. However, article damage is nevertheless a problem with water jet pumps if attempting to achieve the lift height required for many applications because of the high degree of turbulence and the high pressure gradients within the jet injection chamber of the conduit causing flesh damage and disintegration of more delicate marine life such as shrimps and crabs.
The present invention is directed to providing an improved pumping system for such applications and, more particularly, a pumping system that effectively utilizes the lift capability of a water jet pump and, in fact, increases that capability while greatly reducing the article damage experienced in water jet pumps operated at comparable jet velocity.
A further object hereof is to devise an improved pumping system achieving the described results at relatively low cost and without unduly bulky apparatus requirements. A related object is to provide such a system which is relatively easy to install, relatively light in weight and uses components that can be made stowable and readily moved about for assembly and disassembly aboard fishing vessels, and in similar applications.
A further object hereof is to improve the efficiency of jet pumps, particularly jet pumps when used for pumping liquid-borne solid articles. It is a further object to minimize wall abrasion damage of solid articles being pumped.